I have a WaterFurnace Envision closed loop geothermal HVAC system that was installed in 2010. Yesterday during near record cold temperatures in IN, my power flickered and the furnace stopped blowing air, the low pressure light was flashing on my furnace and the two zone thermostats indicated "fault" and there was no heat or airflow. After powering down the furnace a couple times, it started blowing warm air, the status light on the furnace is now flashing green as it should be and the low pressure light is no longer on/blinking, the thermostats both indicate "stg1+2" with the +2 flashing. I assume this means I am now using auxiliary heat. I have heat but since powering back on, the furnace is emitting a loud hum that I have not heard before. It has been constant for nearly 24 hours. Happy to have heat but concerned I may have a problem developing. Would the auxiliary heat cause this noise?